Evening Time Trials

1/5/2018

Now May has started, the weather has laughably not improved at all. But with this “increase” in temperature and daylight the evening time trials have begun. In Warwickshire there was quite a good scene for it, with at least two a week and with some searching I’ve found Lancashire also has the buzz.

Now I’ve always been alright at time trials, I’m good at the sustained effort they require and having several years’ experience I’ve got good at pacing and reading the roads, taking the optimal lines where possible etc. However, I’m on a new bike frame and still adjusting from my (much) larger winter bike so need to adapt and get used to the TT bars. It’ll come with time but I feel that I was struggling to get the power into the pedals and was over 20W down on what I’d expect to do for 20 minutes. I know the power is there as I did 355W for 20 minutes 40km into a 120km training ride the other week, just need to get it out in a TT.

This week I happened to do two TT’s, the first was Rossendale RC on Tuesday evening. I rocked up in my fresh Fat Lad at the Back skinsuit to the Hapton Inn to find only one other rider who like me was puzzled where the organisers were. After 10 minutes sat out shivering in the cold the most typical old cycling Don rocked up to get the race organised. I paid my £3 entry, received number 3 and snuck into the toilets to adorn my number into the no-pinz pocket.

The course is 2.5 laps of a quiet A road through Hapton and is not a quick course. The surface is brittle, coupled with 5 roundabouts and a reasonable hill it’s very hard to get up to a consistent pace. I ended up trying to maintain a hard tempo on the climb and attempting to recover/stay tucked in for the descent. At points I was going over 63kph which can be a bit daunting on an unfamiliar position. Alas, I kept focused but with the cold, felt very stiff and never really felt good. With the nature of the course I could measure my position against the other riders easily and could see I was gaining each lap. Having just passed the 2 lap mark I caught my 2 minute man and pushed onto the finish.

I wasn’t really pleased with my effort, I was cold, stiff and averaged around 325W which is 30W less than I was planning on riding at. Now the course didn’t suit a power PB but I just couldn’t get the effort out. I did manage to come first but there were only 6 riders and I did win by nearly 2 and a half minutes. Still good to get my TT legs going and get used to the position and efforts they require.

With the relative disappointment from Tuesday and the apparent much nicer evening I decided to ride out to Clitheroe and do the North Lancs RC evening 10, on the short Bashall Eaves circuit. The long circuit is home of my 2nd place in the Team Chronomaster RR last season so I knew the roads slightly more than the Hapton course.

Again, the course isn’t quick, it’s very undulating and has several 90 degree turns which kill your speed but I arrived early enough to get in a recon lap and figured out the best lines to take. With the nicer weather (but still chilly) the field was much larger around 30, with riders from NLRC and team Green Jersey. I was keeping my legs warm spinning around the local roads when the sky darkened and the rain came down. Boy was it cold. I was literally on the startline shaking, just couldn’t get warm. Yet again I was in leg warmers for a TT!

Once I got going and got my TT head on I was good though. I began chipping away at my minute man and he was in sight by the end of the first lap. I kept up the power and took good lines around the corners where I could. As there were several short laps, when I came around to the startline I could see a rider who had just set off. A new target to chase. Within a few minutes I pegged them back and started chipping away at their minute man. I lost count of how many riders I caught but kept focused on my effort. Once I got going I felt a lot better than the day before and averaged 346W. Still down on what I wanted but with the corners on the course it wasn’t a bad effort.

I came in 4th place, 10-15 seconds behind 2nd and 3rd but 50 behind the winner. I just can’t compete against those on a full TT setup, but once I get my position sorted I’ll be quicker.

The Numbers

Firstly lets look at the raw data. I’ve got a screenshot of the training peaks summary for each TT. On the left is the Rossendale RC and the right North Lancs. In terms of similarities, my cadence and average heartrate are almost identical, as is the variability index. A cadence of 95 is a little low for me, in a TT I’d expect to be doing around 100-110 rpm but it has been dropping since I moved to a hillier area, so it’s probably a by-product of that. My average heartrate is also very low. Last season my threshold heart rate was 182bpm but I’ve been struggling to hit anywhere near that recently. 168 is really low for me, I think it’s a combination of fatigue as I’m towards the end of a tough block of training and not trying that hard.

Variability index is an algorithm showing how evenly paced the power output for a workout is. The closer to 1 the more evenly paced. Having 1.03 and 1.04 is very good. It doesn’t get much better for a TT

Aerodynamics

Using the Chung analysis from Golden cheetah I can estimate my coefficient of drag. For the plot below there is quite a bit of uncertainty, firstly I didn’t weigh either my bike or myself beforehand so I’m estimating that, as well as the coefficient of rolling resistance. The air density (Rho) should be accurate as it was based on empirical data from the weather forecast. Another cause of uncertainty was the level of wind, both days were pretty windy, so that will again decrease the accuracy. It also rained for most of the second one, so that will skew the results. There weren’t many cars that passed so that is in my favour.

Anyway, ignoring the huge levels of uncertainty, my CDA for the first TT came out at 0.2851 and the second 0.3178. These aren’t too bad actually, if I take the average of 0.30145, it fits what I’d expect for a standard road bike with aero bars on. There is some optimisation to do though; I raced in my training wheels, with lights on by mistake (doh) and I can configure the best slope for the bars the next time I get a still day. There is definitely room for improvement but it gives me a good CDA starting point.

Stress

Looking at the two plots below you can see how my W’ (Battery) decreases through each ride. The red line indicates how, as I ride above threshold my store of energy depletes, while the yellow is my power (smoothed) and grey, the profile.

From the first graph you can really see how I drilled the climb, then recovered significantly on the descent. I was pushing a 50x11 at over 60kph but couldn’t get any more effort out so recovered and kept tucked in. The second is just very inconsistent, you can see how I am surging throughout but have a really big finish. Neither are ideal graphs, what they should look like is this one from a 20 minute hill effort I did the other day. The power is consistent and the W’ line drops at a constant rate. It’s exactly what a flat TT should look like.

Quadrant Analysis

Finally, lets do some quadrant analysis. Quadrant analysis can be used to see what the pedal strokes were like. The plots below show the quadrant analysis for the Hapton TT on the left and the Bashall TT on the right.

The first plot is generally tightly spaced around the centre, showing a good balance of efforts. It much more typical of a TT than the second plot which is much more varied. The second plot has a lot of markers in Quadrant I (top right) which indicates high force and high velocity. It shows I did a lot of sprinting and supra-threshold efforts, much more than the first plot. Again, it’s a sign of the inconsistency of the effort. In general the plots should be more similar to the example TT from Training peaks below. You can see the general shape is there but is fundamentally skewed into the right quadrants by the courses.